Electrical power converters are used to meet specialized current and voltage requirements of a load with the available source power. For example, chains of light-emitting diodes (LEDs) may require a certain DC voltage and current for proper operation. LED chains may typically be powered with two-stage control gear including an AC-DC voltage converter and a DC-DC current converter, typically a step-down or buck converter with a lower output voltage than input voltage.
An LED chain controller may be either analog or digital. An analog controller causes the illumination to be proportional to the current, which has the advantages of simplicity and fast response time. However, the response of illumination to current is non-linear, and the frequency spectrum of the illumination also varies with current, causing the color of the light to change with the brightness. Digital DC-DC current converter controllers are thus preferred for many applications. A digital controller may adjust the illumination of the LED chain by switching the current on and off at a high rate, preferably fast enough to be below the threshold of detection by human perception, such that the human brain only detects constant illumination. If the switching frequency fails to be faster than the limits of human perception, though, people become able to perceive a noticeable flickering of the light.